EV71 and Acute Flaccid Paralysis

By Amesh A. Adalja, MD, FACP, May 31, 2013

Enterovirus 71 (EV71), first discovered in 1969 in California, is increasingly recognized as a pathogen that could cause severe disease and widespread infection during periodic outbreaks. A recent report on ProMED announced that the acute flaccid paralysis (AFP) surveillance program in Australia had identified EV71 in 36% of AFP cases referred, a finding that highlights the potential virulence of this emerging pathogen.1

Enteroviruses

Enteroviruses are a genus of viruses in the picornavirus family. The genus is subdivided into 5 subgenera: polioviruses, group a coxsackieviruses, group b coxsackieviruses, echoviruses, and enteroviruses.

These viruses are transmitted via contact with gastrointestinal or respiratory secretions and cause a variety of disease states ranging from polio to hand-foot-and-mouth (HFM) disease. There are no antivirals to treat these infections and a licensed vaccine is available only for the polioviruses.2,3

EV71

EV71 was first isolated from children with aseptic meningitis and encephalitis, but the virus has also been linked to major outbreaks of HFM. A 2-year outbreak in China (2007-2009) was responsible for hundreds of thousands of cases and hundreds of deaths and prompted a nationwide hygiene and hand-washing campaign.4,5

HFM typically presents with vesicles and pain in the oral cavity with concomitant cutaneous lesions. Aseptic meningitis and encephalitis are severe manifestations of infection. Paralysis as result of EV71 infection has been a recognized complication of EV71 since at least 1984.6

In the US, from 1970-2005, EV71 ranked as the 27th most common enterovirus reported to the CDC, and in 1994 it was the 5th most common reported enterovirus. Those younger than 5 years of age constituted the vast majority of reported cases.7

The Future of EV71

Polio’s partial eradication has supplanted it as a cause of AFP from all but 7 countries (Nigeria, Pakistan, Afghanistan, Niger, Chad, Kenya, Somalia), so surveillance for AFP is heightened. The role of EV71 may be magnified because of increased detection and because the virus may exploit a niche that had been filled by poliovirus. Because of its ability to cause severe disease and widespread outbreaks, EV71 vaccine development has become a high priority.